Robert K. Kuhn
CRX Owners Group President (http://www.crx.org/southcal)
1990 Honda CRXsi (http://www.hooligan.cc)
ICQ # 3714283 (nickname: godzilla)
Julian Drive (San Diego County) - February 22, 2003
http://www.crx.org/southcal/events.html
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To: [EMAIL PROTECTED]
From: Citizen Kang <[EMAIL PROTECTED]>
Subject: re: [hooligan racing] engine running rich
Date: Fri, 07 Feb 2003 19:27:52 -0800
Reply-To: [EMAIL PROTECTED]
Oxygen sensors work by producing a voltage between 0 and 1 volts when up to operating temperature. There are one wire, three wire, and four wire oxygen sensors in common use today. It shouldn't take much investigation to find out which one is which (three wire sensors have one ground, one 12V, and one signal wire, while four wire sensors have two grounds). When the engine is warmed up and running, sample the voltage. If the readings max out at, say, 0.8 volts or won't go below, say, 0.3 volts, you have a bad oxygen sensor. Also, the reading should normally fluctuate up and down when the engine is warm and the computer is in closed-loop mode. The reading should fluctuate back and forth quite a bit, and should go rich (ie: 0.8-1.0 volts) when you give it a little gas. If the readings fluctuate slowly, or the voltage doesn't quickly climb when you throttle up, you have what is called a "lazy" oxygen sensor. "Lazy" isn't quite as bad as "bad", but should be replaced anyway. The circuit itself can only be tested for continuity, and anything beyond that requires an actual engine analyser. You can't simply adjust the mixture with a malfunctioning oxygen sensor since the computer is designed to perform all of the mixture adjustments itself. Tampering with any sort of mixture control will simply cause the computer to compensate even more. Nine times out of ten, your problem lies within the oxygen sensor itself.
MAP stands for Manifold Atmospheric Pressure -- and that is what a barometric sensor measures. They have three wires running to them: one for ground, one for a reference 12V signal, and one for the output signal. I can't remember the range but a volt meter hooked up to the output should show a steady signal at idle and a quick change when you snap the throttle. If you can run an actual vacuum gauge at the same time, you should be able to verify the signal shifts as the vacuum changes. Most cars nowadays substitute a MAF sensor for the MAP sensor. MAF sensors -- short for Mass Airflow Sensors -- eliminate the need for both a MAP sensor and an Air Charge Temperature sensor (the other sensor you're probably referring to). MAF sensors use a tiny heated wire suspended in the airflow entering the engine. As air moves past the wire, it cools. The sensor attempts to keep the wire temperature the same and therefore must increase the current feeding the tiny wire. It is this signal that the computer reads. Mass airflow takes into account air temperature, air density, and air velocity to determine precisely how much air is actually entering the engine at any one time.
- -----Original Message-----
- From: Andrew Y. Chan [mailto:[EMAIL PROTECTED]]
- Sent: February 7, 2003 2:04 PM
- To: [EMAIL PROTECTED]
- Subject: [hooligan racing] Engine running rich
- Hey all,
- So Im finally getting around to taking care of some problems Ive been having with my car. For now I wanted to see what advice you guys could give on my engine running too rich. From the car codes that were associated with the Service Engine Soon (SES) light, I need to check either the O2 sensor or the circuit itself. My question is, how does one go about testing either the sensor itself or the circuit? Or would just adjusting the gas/air mixture also solve my problem? Is this recommended?
- The second code I got was that the baro (barometric pressure) sensor has low voltage. How do I go about testing this? Ive read some where that on some cars, the baro sensor is part of the MAP sensor. However, on my 1992 Saturn SL2 they seem to be separate sensors.
- Im in the process of looking for my trusty old Chiltons guide, but any advice is greatly appreciated. TIA!
- andrew
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